What Are LCD TVs?

Otherwise known as liquid-crystal-display televisions, LCD TV sets are using liquid-crystal displays to produce images and scenes. Though, originally costs were to high to offer the technology to consumers at a reasonable price, those same costs fell and now LCD technology is widespread. You will find yourself hard pressed to find a place that doesn’t have some sort of a LCD display all around you. LCD technology also offers a larger range of sizes than its predecessor cathode ray tube or CRTs.

This was first noticed in 2007, when LCD technology took over all other options for TVs at the time. That includes plasma televisions, CRT televisions, and rear-panel televisions. There have been some changes over the years and LCD have become better, but not without fault. The technologies that address these issues are the OLED, FED and SED technology alternatives, but compared to LCD the technology is not as widespread or cost-effective. Thus, the technology cannot offer a reasonable price to consumers.

Understanding LCD TVs

LCD Basics

LED BULBToday many LCD TVs use  light-emitting diodes or LEDs as their backlighting system. This is different than the cold cathode fluorescent lamps or CCFLs that used to be used more commonly just a few years ago. To understand how the picture is created you need to understand how the TV is built or rather, parts are arranged. Ten of thousands of LCD shutters are arranged in a grid. These shutters are told to open and close at specific times to allow light to pass through. White light to be exact. Filters are paired to each shutter to make what is considered a shutter-filter. The filter helps to remove all colors from the original white light except Red, Green, and Blue. This makes the RGB many people are used to seeing or hearing about. This essentially is considered to be a sub-pixel. When each sub-pixel is combined with another it makes what is considered an actual pixel.

The shutters in the shutter-filter combo, are to help control the flow of light from the white source. They do this through the way they are made. On the top and bottom are plates that are bent at right-angles. Light cannot pass or rather, cannot pass through these plates very well. This will make the display appear black or off. This is important to know because it helps with the “Liquid-Crystal” to help produce an image.

Liquid crystal diodes get their name from how they work on a very basic level. They are solids that have traits of a liquid. Though not in the randomness of a liquid, but rather that it can bend and be twisted. This is important to remember because when a voltage is applied, the bending can be controlled in conjunction with the shutters. Thus offering control over which colors are seen when viewing the television.

This is the same across types of display that use a variation of LCD technology. Whether it is a Vertical Alignment variation offers a worse viewing angle to help produce a higher contrast ratio or the In-Plane Switching (IPS) variation that offers a better viewing angle at the cost a slower response time. As more of the technology is either invented or made more available to consumers, the TVs become more of a “pick your poison” situation.

 

A Little About Pixels

One of the problems with early LCD TVs were the pixels and how they were addressed. See, voltages needed to adjust the shutter-filter combo was maintainable, but was too low to allow for them to readjust, or un-twist as needed. This results in what is known as ghosting and slow response times. This meant a very poor handle on motion and is essentially a trail of the picture left behind as the new picture comes into your field of view. This was fixed by the active-matrix that modern day LCD TVs use now.

The Display’s Parts

Think of your favorite sandwich. How do you layer it to taste the best? Now think of LCD TVs as your sandwich, and instead of taste the best, how do you make it work the best?

A typical TVs will have two glass sheets that make up

the front and back of the display. Though, the glass used to be replaced with plastic. It depends on the manufacturer and their preferred process.

The organization will follow as a polarizing film, a glass sheet, the active matrix pieces with electrodes, and then the director. It is important that the sheets within the TV are kept at a precise distance from one another. This is so the liquid-crystals can better do their job to produce an image or moving scene. A huge step is also with the manufacturing of active-matrix components. These have a higher than preferred failure rate and if a picture is not deemed good enough, the panels thrown away. Then from scratch they begin.

Once is all said and one the shutters are combined with the remaining panels and pieces. This step ss where many TVs produce their dark spots. See, the backlight can usually be handled by one lamp in smaller TVs, but as TVs become larger one lamp will not do. Thus evenly lighting the display can be a hassle and tough to maintain.

How Well Do They Perform

LCD TV Efficiency

Let’s just say they are not the most efficient in terms of energy use. This is why you’ll see many manufacturers list the TV’s energy use on the side of the box. It could certainly be better, but let me explain why.

When the white light is first produce, the shutter in the shutter-filter combo from earlier, blocks much of the light coming through. Then the filter removes the remaining pieces of light from the white light to leave only the Red, Green, and Blue. The Red Green and Blues are not taken evenly, but rather in specific amounts to produce the correct color for our eyes to see when it comes into our field of view. So, imagine that you start with 100% white light and then 50% is removed and then another 25% is removed to leave only 25% of the original white light.

For the above reason a backlighting system must be strong enough to make sure that they can remove the light as needed.

This has been an attempt to fix this issue through what is known as dynamic lighting. Many TVs these days have a system built into the TV to help handle this issue. The most basic explanation for me to use is that, as the image or scene is displayed by the TV, it will scan itself to look for areas of the TV that are darker than the rest. This is because a TV does not need as much “light” or brightness pouring through to produce that color in that area of the TV. Thus the TV will limit light in that area of the TV and help save a bit of energy.

Sony is a leading producers of TVs that offer a better solution for energy efficiency. They produced a television that produce a surprisingly bright image that was using only one-tenth (1/10) of the energy a regular LCD TV would use. That would put the TV around 14 W.

Picture Value

Contrast Ratio

LCD TVs for the longest time did not have the reputation of having a great contrast ratio. This is because their shutters and filters allow for slight bits of light to leak through. That affects the contrast ratio in large ways and will prevent a higher contrast ratio from existing in conjunction with these TVs. Granted, they have come a long way and now many of them offer much higher contrast ratios.

To explain further a contrast ratio is how well the TV can display a black (darker) color apart from a white (lighter) color. This is important for a clear and crisp picture, but is most noticeable in a dark room. Dark colors will looked off or will be hard to see while lighter colors will have lost their luster or look like they’re not that bright at all. This is why many of my reviews mention the contrast ratio as it is a huge part of a TVs value on whether or not you should purchase it.

Though technology has improved by moving from CCFL backlights towards LED backlighting systems. Full-Array backlighting is one such example. The LED lights only light up a small part of the screen. This allows the dynamic lighting a better control over the brightness and picture value overall. Edge-Lit displays are another story as they have LED light only placed around the edges of the TV. They instead use a panel covered essentially in bumps that reflect light. This is cheaper to produce though leading to more TVs have this technology.

Color Gamut

As explained earlier, a white light in watered down by a shutter to assist the filter. The filter then further waters down the white light to ensure the correct amounts of Red Green and Blues are remaining to produce the correct color when the TV’s image or scene comes into our field of view.

Motion Handling and Response Time

A decent response time by today’s standard is going to come in around 20 ms. This will allow relatively smooth 60 frames per second scenes when viewing a TV. This was not always the case as many TVs in the early days of LCD technology was well over 200 ms. This is not a good number or even close. Let’s consider that a bad number for the rest of time.

This was until a company called NEC realized that the crystals used in the TVs needed another look. They noticed that the liquid-crystals that spin need some time to spin. On the other hand they stop on dime, but that time before was important. Through NEC’s process of increasing voltage during the “wind-up” period, we were able to produce clearer scenes of moving content. Before scrolling through text was a jumbled blur, but now it maintains a clear and crisp picture. The term coined a phrase “Overdrive” by NEC which is still used to this day.

You’ll also see what is called “super-sampling”. Essentially, the blur you see when looking at a TV is taking place during a transition period. This is fixed by effectively doubling the refresh rate and placing “fake” frames between each “real” frame to produce a smooth image or scene.

LCD Competition

OLED, FED, and SED TV sets are currently the biggest competitors to modern day LCD TVs. They offer some huge benefits such as the below:

  • Better viewing angles
  • Higher brightness
  • Better Contrast ratios

On the other hand these sets are harder to produce and thus have not been made widely available at a decent price to consumers. You will see LG and Samsung releasing some OLED TV sets, but not for a very good price unfortunately.

Save The Environment

A massive part of LCD TVs are the materials used on the inside of their parts. These materials can cause harm to the environment if not handled properly. The biggest is Nitrogen Trifluoride. It is a very dangerous greenhouse gas with a long half-life. Otherwise known to contribute to global warming. Nitrogen Trifluoride is also known as “The Missing Greenhouse Gas”. I warn you to be careful if one of your LCD TVs break down or have broken in some major way. Contact your local waste companies to help dispose of them properly. Often times many companies will help you free of charge or will pay you to get rid of the product as they can salvage the working pieces while properly disposing of the dangerous materials.

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